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v/vlib/sync/once.v

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module sync
import sync.stdatomic
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pub struct Once {
mut:
m RwMutex
pub:
count u64
}
// new_once return a new Once struct.
pub fn new_once() &Once {
mut once := &Once{}
once.m.init()
return once
}
// do execute the function only once.
pub fn (mut o Once) do(f fn ()) {
if stdatomic.load_u64(&o.count) < 1 {
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o.do_slow(f)
}
}
fn (mut o Once) do_slow(f fn ()) {
o.m.@lock()
if o.count < 1 {
stdatomic.store_u64(&o.count, 1)
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f()
}
o.m.unlock()
}